The present invention relates to a developing device and an image forming apparatus.
A conventional developing device is used in an image forming apparatus such as a printer, a copier, and the likes. In the conventional developing device, an optical detection unit is provided for detecting a remaining amount of toner stored in a storage unit as developer. In this case, a transparent window member is disposed in a wall of the storage unit retaining toner, so that a remaining amount of toner is detected using light passing through the window member (refer to Patent Reference).    Patent Reference Japan Patent Publication No. 2003-162138
In the conventional developing device, a remaining amount of toner is detected at one point in the storage unit. Accordingly, when toner has an uneven distribution in the storage unit depending on a pattern of an image to be formed, it is difficult to accurately detect a remaining amount of toner.
In order to securely prevent toner from being supplied to a developing roller even in a case of an insufficient amount of toner, it is arranged to detect a remaining amount of toner with a certain margin, considering a situation in which a remaining amount of toner is not accurately detected. Accordingly, a toner cartridge is prompted to replace at a relatively early stage. As a result, even though a toner cartridge still retains a sufficient amount of toner, the toner cartridge is replaced with new one, thereby wasting toner.
In view of the problem described above, an object of the invention is to provide a developing device and an image forming device, in which it is possible to solve the problems of the conventional developing device. The developing device includes a plurality of window members disposed on a plurality of optical paths for detecting a remaining amount of toner. Further, a cleaning unit is provided for periodically cleaning the window members in cycles shifted by a specific phase. Accordingly, even when toner retained in a storage unit has an uneven distribution, it is possible to accurately detect a remaining amount of toner, thereby conserving toner.
Further objects of the invention will be apparent from the following description of the invention.